Journal of Psychosomatic Research 79 (2015) 62–68
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Journal of Psychosomatic Research
A Breathlessness Catastrophizing Scale for chronic obstructive pulmonary disease☆ Brahm K. Solomon a,⁎, Keith G. Wilson b, Peter R. Henderson b, Patricia A. Poulin c, John Kowal b, Douglas A. McKim d a
School of Psychology, University of Ottawa, Canada Department of Psychology, The Ottawa Hospital Rehabilitation Centre, Canada Department of Psychology, The Ottawa Hospital, Canada d Department of Medicine, University of Ottawa, Canada b c
a r t i c l e
i n f o
Article history: Received 17 July 2014 Received in revised form 22 November 2014 Accepted 25 November 2014 Keywords: Catastrophizing Chronic obstructive pulmonary disease Disability Rehabilitation Depression Anxiety
a b s t r a c t Objective: Catastrophizing about breathlessness may be related to disability in patients with chronic obstructive pulmonary disease (COPD), but assessment options are limited. This study reports the initial validation of a 13item Breathlessness Catastrophizing Scale (BCS). Method: Pulmonary rehabilitation inpatients completed spirometric, functional performance and questionnaire assessments at admission (N = 242) and discharge (n = 186). Results: The BCS comprised a unifactorial scale that demonstrated excellent internal consistency (Cronbach's alpha = .96) and correlated with measures of anxiety sensitivity, depression, and self-efficacy, but not with performance on walk and stair-climbing tests. BCS scores improved robustly with rehabilitation, approaching a medium effect size (d = .43), and demonstrated a modest association with enhanced performance in a stairclimbing test of exercise tolerance. Conclusion: The BCS is a reliable measure of catastrophizing in severe COPD that has good convergent validity and sensitivity to change. Its association with functional performance requires further investigation. However, it appears that a high level of catastrophizing about breathlessness is not a barrier to functional improvement with inpatient pulmonary rehabilitation. © 2014 Elsevier Inc. All rights reserved.
Introduction Chronic Obstructive Pulmonary Disease (COPD) is a progressive degenerative lung disease that causes cough, sputum production, and disabling breathlessness [1]. As of 2010, COPD was identified as the fourth leading cause of death in the U.S. and the sixth leading cause of years lived with disability [2]. For those COPD patients who are limited functionally by dyspnea, the recommended treatment includes pulmonary rehabilitation to improve symptom management and participation in activities of daily living [1]. According to the WHO-endorsed standards outlined by Global Initiative for Chronic Obstructive Lung Disease (GOLD) [1], spirometric assessment of lung function is required to confirm a
☆ Clinical and research work was conducted at The Ottawa Hospital Rehabilitation Centre, Ottawa, Ontario, Canada. ⁎ Corresponding author at: School of Psychology, University of Ottawa, Department of Psychology, The Ottawa Hospital Rehabilitation Centre, 505 Smyth Road, Ottawa, ON K1H 8M2, Canada. Tel.: +1 613 422 1870; fax: +1 613 737 7056. E-mail address: [email protected] (B.K. Solomon).
http://dx.doi.org/10.1016/j.jpsychores.2014.11.020 0022-3999/© 2014 Elsevier Inc. All rights reserved.
diagnosis of COPD. Spirometry, however, is often a poor predictor of a patient's level of disability [3]. In contrast, psychological factors have often been related to functional outcomes in this population [4]. Depressive symptoms, for example, have been associated with decreased mobility and functional status [5–10], as well as more frequent and longer hospital admissions [9]. Similarly, anxiety has been related to decreased physical health, exercise performance [3], functional performance status [3,11,12], and more frequent hospitalization [3]. Recently, research has begun to expand beyond broad psychopathological constructs, such as depression and anxiety, into particular affective and cognitive processes that may influence how one attends and responds specifically to the symptom of dyspnea [13, 14]. It has been proposed that breathlessness catastrophizing is one such cognitive process that warrants further investigation [7, 15–17]. Catastrophizing is an exaggerated negative cognitive orientation toward noxious stimuli and experiences, characterized by rumination about those experiences, magnification of their threat value, and perceived inability to control them [18]. It has been associated with measures of disability in other chronic medical conditions,
B.K. Solomon et al. / Journal of Psychosomatic Research 79 (2015) 62–68
particularly chronic pain [19–23]. In some studies of individuals with chronic pain, catastrophizing has been found to be more strongly correlated with disability than the pain itself [24,25]. This has contributed to the development of a fear-avoidance model of disability [26]. The fear-avoidance model proposes that when a symptom is appraised as threatening, the individual may respond with fear, hypervigilance, and avoidance of activity that could trigger it. In the long term, these responses are counterproductive for rehabilitative efforts and can lead to further disability [26]. Indeed, catastrophizing has been identified as a prospective marker of risk for severe disability in chronic pain [27,28], in part leading to the recommendation that the assessment and treatment of catastrophizing should be a regular part of patient care [29,30]. The conceptual link between catastrophizing and disability can perhaps be extended to other medical conditions that feature a prominent primary symptom. In the case of COPD, for example, it would be expected that patients who catastrophize about dyspnea would similarly become fearful of, or hypervigilant to, the experience of breathlessness, perhaps leading to an avoidance of activities that might trigger shortness of breath [31–33]. To date, however, speculation about the importance of catastrophizing in COPD has focused largely on its relevance to the emergence of panic symptomatology that occurs in some patients [16,34]. More generally, a fear-avoidance model applied to COPD would suggest that individuals who catastrophize would engage in physical therapy at suboptimal levels and exhibit a more general unwillingness to engage in programs that are heavily focused on exercise [14]. However, there are limited options for assessing catastrophizing in individuals with COPD, so there has been little formal investigation of these hypotheses. At present, the Interpretation of Breathing Problems Questionnaire (IBPQ) [35] is the sole catastrophizing measure available for use with individuals with COPD. Its format makes it difficult to complete in a clinical setting, however, and it has seldom been used since its development in 1999 [17,36–38]. The IBPQ presents 14 scenarios (e.g., “You are in a smoky pub and your chest begins to feel tight.”) and asks respondents to answer qualitative questions that are subsequently scored by raters for degree of catastrophizing. IBPQ items have been found to correlate with measures of anxiety [35], although not consistently [36]. Moreover, no studies have examined the association between IBPQ scores and functional measures. In the present study, the Breathlessness Catastrophizing Scale (BCS) is proposed as an alternative measure offering several advantages. First, the BCS items directly reflect experiential aspects of catastrophizing (e.g., “There's nothing I can do to reduce the intensity of the breathlessness”). Second, qualification as catastrophic thinking is not limited to an increase in anxiety, illness, or death. Third, the BCS is practical for clinical use, with each item requiring only a single quantitative rating. Finally, the BCS is a modification of the well-established Pain Catastrophizing Scale (PCS) [18], which represents the standard in the assessment of catastrophizing among patients with chronic pain. Given the emerging focus on catastrophizing and anxiety-related concerns in COPD, the goals of the present study were to: (1) validate the scores on the BCS in a relatively large sample of patients undergoing pulmonary rehabilitation for COPD; (2) examine the relationship between breathlessness catastrophizing and measures of anxiety sensitivity, depression, self-efficacy, lung function, and performance in structured physical tasks; (3) examine whether breathlessness catastrophizing changes with participation in a pulmonary rehabilitation program; and (4) evaluate whether breathlessness catastrophizing is related to change in other rehabilitation outcomes. Specifically, we hypothesized that individuals with high levels of catastrophizing would show less improvement in psychological and physical function following interdisciplinary treatment.
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Method Participants The study was approved by the Ottawa Health Science Network Research Ethics Board. Participants were 242 patients with COPD admitted to an inpatient, interdisciplinary pulmonary rehabilitation program at The Ottawa Hospital Rehabilitation Centre (TOHRC; Ottawa, Canada). In order to be eligible for admission to the program, patients had to be referred by a physician, 18 years of age or older, seeking to improve quality of life limited by shortness of breath, cognitively able to learn how to better manage the condition, and meet at least one of the following criteria: (1) FEV1 ≤ 70%; (2) hospitalized recently or visited an emergency department due to dyspnea; (3) willing and able to initiate and maintain an exercise program; (4) using supplemental oxygen. Patients admitted to the program were included in this study if they had completed a BCS at admission. Design Chart reviews were conducted for eligible patients who participated in the program between 2007 and 2011. Extracted data included assessment of lung function, functional measures of exercise performance, and psychometric measures of catastrophizing, anxiety sensitivity, depression, and COPD self-efficacy. Measures completed at both program admission and discharge were collected. Pulmonary rehabilitation program Patients participated in a structured inpatient interdisciplinary pulmonary rehabilitation program based on GOLD and Canadian Thoracic Society guidelines [39,40]. The program took place over four 5-day weeks, with patients returning home over weekends. Measurements Spirometry Forced vital capacity (FVC) is the volume of air that can forcibly be exhaled after full inspiration, measured in liters. Forced expiratory volume in one second (FEV 1 ) is the volume of air that can be forcibly exhaled in 1 s, after full inspiration. These values were measured using a Profiler and CPSF/D spirometer (Medical Graphic Corporation; St. Paul, MN, US). Predicted values for these measurements (FVC%, FEV 1 %) were based on reference values of pulmonary function tests of a Canadian sample [41]. Exercise performance Six-Minute Walk Test The Six-Minute Walk Test (6MWT) is the standard measure of functional capacity used in pulmonary and rehabilitation studies [42]. The test requires a 100-foot flat, hard surface on which individuals can walk unaccompanied. Patients are asked to walk as far as possible in 6 min, slowing, stopping, or resting, as needed. The primary outcome of interest is the distance walked. Contraindications include chest pain, intolerable dyspnea, leg cramps, staggering, diaphoresis, and pale or ashen appearance [42]. Contraindications were common in this sample, and only 98 patients completed the 6MWT at admission. Non-Stop Walk Test The Non-Stop Walk Test (NSWT) is an alternative measure used in the pulmonary rehabilitation program at TOHRC. In line with the
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findings of the developers of the 6MWT [43], longer intervals are considered preferable, when feasible. Patients are asked to walk for 20 min and are encouraged to use a comfortable, self-selected pace with slowing, but no pauses, rests or actual stops. Again, the primary outcome is the distance walked. All 242 patients completed this test at admission. Stair climbing Stair climbing is a standard measure of functional capacity used in cardiac, pulmonary, and rehabilitation studies, and it is considered reflective of a primary activity of daily living and mobility [44]. The present assessments required that the patient climbs as many steps as possible before having to stop because of dyspnea. The total number of stairs climbed was the primary outcome, with a maximum score of 49.
demonstrated excellent internal consistency (Cronbach's α = .86–.89) and test–retest reliability (r = .84) (Kroenke, Spitzer, & Williams, 2001). Cronbach's α for the current sample = .87 (average inter-item correlation = .33). COPD self-efficacy The COPD Self-Efficacy Scale (CSES) [54] is a 34-item self-report questionnaire that assesses individuals' perceived confidence in their ability to manage or avoid breathing difficulties in various situations. Each item is rated along a five-point scale, ranging from 1 (Very Confident) to 5 (Not At All Confident). An overall measure of self-efficacy can be derived as a total score, with higher scores reflecting lower self-efficacy. Internal consistency (Cronbach's α of .95) and test-reliability (r = .77) were reported to be satisfactory [54]. Cronbach's α for the current sample = .96 (average inter-item correlation = .42).
Questionnaire measures Data analysis Breathlessness catastrophizing The BCS was adapted from the PCS [18] by replacing the term “pain” with “breathlessness,” where relevant. The resulting measure is a 13item scale that asks respondents to rate “the degree to which you have these thoughts and feelings when you are experiencing breathlessness” (e.g., “I feel I can't go on”; “It's terrible and I think it's never going to get any better”). Each item is rated on a five-point scale, ranging from 0 (Not At All) to 4 (All The Time). The original PCS has been found to have high test–retest reliability (Pearson's r = .92) [18] and good internal consistency (Cronbach's α s between .85 and .91) [18]. The PCS has been found to have a moderate correlation with selfreport measures of anxiety (r = .32) [45] and anxiety sensitivity (r = .61) [46]. Anxiety sensitivity Anxiety sensitivity is the fear of physiological symptoms of anxiety due to the belief that they are harmful. Studies suggest that anxiety sensitivity promotes hypervigilance to bodily sensations and fearful interpretations of symptoms when they occur [47,48]. Among patients with COPD, anxiety sensitivity has been found to predict greater dyspnea-related activity avoidance, even after controlling for diagnosed anxiety disorders and degree of pulmonary dysfunction [31]. The Anxiety Sensitivity Index (ASI) [34] is a 16item self-report questionnaire that assesses individuals' fear of anxiety-related symptoms. Each item is rated on a five-point scale, ranging from 0 (Very Little) to 4 (Very Much). Overall, the ASI has very good construct validity [49], internal consistency (Cronbach's α of .82–.91) [50], and test–retest reliability over a three-year period (r = .71) [51]. Cronbach's α for the current sample = .93 (average inter-item correlation = .45). Depression During the period of data collection, the respiratory rehabilitation program used two different measures of depression at different times. For part of the sample (n = 124), the 21-item Beck Depression Inventory-II (BDI-II) [52] was used to assess the presence and severity of depressive symptoms. Responses to each item are rated on a 4-point scale, ranging from 0 to 3, with higher scores reflecting more severe symptomatology. The BDI-II has been found to have high internal consistency (Cronbach's α = .91) [52], as well as good convergent validity when correlated with other measures of depression. Cronbach's α for the current sample = .88 (average inter-item correlation = .27). For the rest of the sample (n = 118), depressive symptoms were assessed using the 9-item Patient Health Questionnaire (PHQ-9) [53]. On this measure, respondents rate how often they have been bothered by each of several diagnostically relevant symptoms. Responses are recorded on a 4-point scale, ranging from 0 (Not At All) to 3 (Nearly Every Day). The PHQ-9 has
Statistical analyses consisted of five distinct parts. First, comparisons were undertaken between program completers and noncompleters, using chi-square analyses for categorical measures and independent samples t-tests for continuous ones. Second, for initial construct validation of the BCS, a principal component analysis (PCA) was conducted to examine the underlying factor structure of the catastrophizing items. PCA is considered to provide the best explanation of data variance without requiring a priori assumptions about the nature of the factor structure [55]. Third, to assess the relationship between breathlessness catastrophizing and other baseline measures, a series of bivariate correlations were examined. Fourth, to identify the extent of change in breathlessness catastrophizing and other measures following pulmonary rehabilitation, data collected from program completers at admission and discharge were compared using paired-samples t-tests. Fifth, subgroups were created based on BCS scores at admission. Clinically, BCS scores are likely to be most informative for identifying individuals who are highly prone to catastrophizing. Hence, we selected patients in the upper quartile of BCS scores and compared them with all others in the sample [56]. Admission and discharge data were compared using 2 (Group) X 2 (Time) Analyses of Variance (ANOVA). All analyses were conducted using SPSS version 20. Significance was set at p b .05. Results Sample characteristics Of the 242 patients (n = 126 women, 52%), most had very severe (Stage IV: n = 140, 58%) or severe (Stage III: n = 70, 29%) COPD, based on FEV1 percent predicted staging [1]. Baseline characteristics of the sample are provided in Table 1. Fifty-six patients (23%) did not complete the program. No significant differences were demonstrated between treatment completers and noncompleters. Validation of the BCS Item-level analysis Although individual distributions varied across items, each value on the 5-point scale was used for all 13 items. The mean, standard deviation, and itemtotal correlation for each question on the BCS are presented in Table 2. Notably, there were no negative item-total correlations. Therefore, no item detracted from the cohesiveness of the total BCS scale. Across the 13 items, Cronbach's alpha was .96 (average inter-item correlation = .64), demonstrating excellent internal consistency. The average total score was 18.25 (SD = 11.76), and the score distribution ranged from 0 to 52, the lowest and highest scores possible. There were seven individuals with scores of 0, suggesting no breathlessness catastrophizing in less than 3% of program participants. The overall average item rating on the 13-item scale was 1.44, which falls between “slight” and “moderate” agreement. Question 8 (“I anxiously want the breathlessness to go away”) was the most highly rated (M = 2.05), whereas question 5 (“I feel I can't stand it anymore”) was rated lowest (M = 1.09).
B.K. Solomon et al. / Journal of Psychosomatic Research 79 (2015) 62–68
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Table 1 Baseline characteristics of patients. Total sample (N = 242) Characteristic
M
SD
Age (years) Sex Female Male FEV1, % predicted FVC, % predicted COPD severity Stage I Stage II Stage III Stage IV Oxygen prescription 6MWT, ma NSWT, m Stairs, steps BCS ASI BDI-IIb PHQ-9b CSES
66.1
11.2
n
126 116 41.0 60.7
Completers (n = 186) %
92.6 363.6 13.7 11.8 11.6 7.7 4.7 14.2
SD
65.8
10.7
124b 118b
%
101 85 41.5 61.3
0 32 70 140 58 98a
Non-completers (n = 56)
n
52.1 47.9
19.5 18.6
311.9 447.9 20.1 18.2 21.7 12.0 5.7 106.7
M
SD
67.0
13.2
54.3 45.7
19.9 19.0
39.3 58.7
0.0 13.2 28.9 57.9 24.0 308.7 451.7 19.7 18.7 22.3 11.4 5.7 106.2
M
0 24 52 110 45 92a
89.9 360.1 13.2 12.2 11.9 7.6 4.2 14.7
%
24 32
42.9 57.1
0 8 18 30 13 6a
0.0 14.3 32.1 53.6 23.2
18.2 17.3
0.0 12.9 28.0 59.1 24.2 326.1 435.4 21.6 17.0 19.6 14.1 5.5 108.2
95b 91b
n
105.4 378.2 15.6 10.2 10.3 7.7 6.2 12.4
29b 27b
Note. FEV1 = forced expiratory volume in one second; FVC = forced vital capacity; 6MWT = Six-Minute Walk Test; NSWT = Non-Stop Walk Test; BCS = Breathlessness Catastrophizing Scale; ASI = Anxiety Sensitivity Index; BDI-II = Beck Depression Inventory-II; PHQ-9 = 9-Item Patient Health Questionnaire; CSES = COPD Self-Efficacy Scale. a Due to clinical considerations not all patients completed the 6MWT. b During the period of data collection, the program used two different measures of depression at different times. Therefore patients received either the BDI-II or the PHQ-9. Factor analysis No constraints were placed on the principal component analysis. The eigenvalue for the first principal component was 8.74, declining sharply to 0.75 for the second. This suggested a one component structure. All items loaded on this single component, with loadings ranging from .73 to .88 (see Table 2).
Relationships between breathlessness catastrophizing and other study variables Demographics Bivariate correlations of BCS with gender and age revealed no significant relationships.
Table 2 Item-level analysis and principal component loadings of the Breathlessness Catastrophizing Scale items.
M
SD
Item-total Correlation
Component Loading
1.48 1.13 1.40 1.36 1.09 1.78 1.23 2.05 1.21 1.34 1.68 1.29 1.64
1.14 1.15 1.26 1.24 1.19 1.28 1.22 1.31 1.22 1.19 1.34 1.17 1.34
0.74 0.75 0.85 0.86 0.81 0.82 0.71 0.76 0.80 0.77 0.83 0.69 0.83
0.78 0.79 0.88 0.88 0.84 0.85 0.75 0.79 0.83 0.80 0.86 0.73 0.86
Breathlessness Catastrophizing Scale Items 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12. 13.
I worry all the time about whether the breathlessness will subside. I feel I can't go on. It's terrible and I think it's never going to get any better. It's awful and I feel that it overwhelms me. I feel I can't stand it anymore. I become afraid that the breathlessness will get worse. I keep thinking of other times I have been breathless. I anxiously want the breathlessness to go away. I can't seem to keep it out of my mind. I keep thinking about how out of breath I am. I keep thinking about how badly I want the breathlessness to stop. There's nothing I can do to reduce the intensity of the breathlessness. I wonder whether something serious might happen.
Note. Cronbach's alpha = .96 (average inter-item correlation = .64). Item ratings ranged from 0 (“Not At All”) to 4 (“All The Time”.)
Table 3 Correlations between measures at baseline.
BCS ASI BDI-IIa PHQ-9a CSES FEV1% FVC% 6MWTa NSWT Stairs
BCS
ASI
– .61⁎⁎⁎ .50⁎⁎⁎ .42⁎⁎⁎ .34⁎⁎⁎ −.12 −.19⁎⁎ −.15 −.11 −.10
– .52⁎⁎⁎ .51⁎⁎⁎ .30⁎⁎⁎ .06 −.08 −.06 −.05 −.12
BDI-IIa
PHQ-9a
CSES
FEV1%
FVC%
6MWTa
NSWT
– .19 .05 .13 −.28 −.09 −.11
– −.04 −.09 .15 .02 −.02
– .60⁎⁎⁎ .29⁎⁎ .12 .03
– .30⁎⁎ .19⁎⁎ .21⁎⁎
– .61⁎⁎⁎ .43⁎⁎⁎
– .56⁎⁎⁎
– b
.36⁎⁎⁎ −.01 −.25⁎ .07 −.07 −.09
Note. N = 242. a Due to program and clinical considerations not all patients completed all measures included here: BDI-II (n = 124); PHQ-9 (n = 118), 6MWT (n = 98). b During the period of data collection, the program used two different measures of depression at different times. Therefore patients received either the BDI-II or the PHQ-9. ⁎ p b .05, two-tailed. ⁎⁎ p b .01, two-tailed. ⁎⁎⁎ p b .001, two-tailed.
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Discussion
Table 4 Change in outcome measures from admission to discharge. Admission Variable FEV1, % predicted FVC, % predicted 6MWT, ma NSWT, m Stairs, steps BCS ASI BDI-IIa PHQ-9a CSES
Discharge
Change
M
SD
M
SD
t
p
db
41.85 62.08 313.04 447.59 20.24 18.13 21.85 11.25 5.76 104.43
20.16 18.15 94.42 362.19 14.12 11.70 12.21 7.76 4.23 18.37
42.67 62.42 344.68 677.50 26.68 13.30 18.85 6.70 2.68 84.02
20.81 18.12 85.75 293.52 19.04 11.50 13.06 6.47 3.32 28.79
1.16 0.35 4.48 12.87 7.65 −6.14 −3.33 −6.08 −6.41 −7.31
.248 .725 b.001 b.001 b.001 b.001 .001 b.001 b.001 b.001
0.04 0.02 0.35 0.70 0.38 0.42 0.24 0.64 0.81 0.85
Note. n = 186. FEV1 = forced expiratory volume in one second; FVC = forced vital capacity; 6MWT = Six-Minute Walk Test; NSWT = Non-Stop Walk Test; BCS = Breathlessness Catastrophizing Scale; ASI = Anxiety Sensitivity Index; BDI-II = Beck Depression Inventory-II; PHQ-9 = 9-Item Patient Health Questionnaire; CSES = COPD Self-Efficacy Scale. a Due to clinical and program considerations not all patients completed all measures included here: 6MWT (n = 92); BDI-II (n = 95); PHQ-9 (n = 91). b d = Cohen's d where .20, .50, and .80 represent small, medium and large effects, respectively. Psychological variables At program admission, BCS scores were moderately and positively correlated with anxiety sensitivity, depressive symptomatology, as measured by either the BDI-II or the PHQ-9, and scores on the CSES, indicating lower sense of self-efficacy at managing or avoiding breathing difficulty (see Table 3). Respiratory function At baseline only FVC% correlated with BCS scores. Although statistically significant, the correlation was small in magnitude (r = −.19, p = .004). There was no association between BCS scores and prescribed oxygen. Exercise performance Breathlessness catastrophizing was not significantly correlated with the baseline measures of exercise performance (all ps N .10). However, both walk tests and the stairs exercise were correlated significantly with one another (ps b .01) and with the FVC%. In addition, performance on the 6MWT was correlated significantly with the FEV1%. Outcome of pulmonary rehabilitation The pre- and post-rehabilitation scores for all measures of respiratory function, exercise performance, and psychological variables are shown in Table 4. From admission to discharge, spirometry did not reveal any significant change in lung function, ps N .05. However, patients improved on all measures of physical and psychological functioning, including scores on the BCS, p ≤ .001. The change in BCS scores approaches a medium effect size, d = .43 [57]. Group comparisons based on BCS scores at admission To examine the clinical relevance of the BCS for rehabilitation in COPD, the subgroup of participants who fell in the upper quartile of BCS scores at admission was compared with the rest of the sample. The scores are shown in Fig. 1. In addition to the main effect of group, F(1, 184) = 138.61, p b .001, η2p=.47, these scores showed a significant main effect of time, F(1,184) = 82.17, p b .001, η2p=.34, indicating an overall decrease following rehabilitation. The Group × Time interaction was also significant, F(1, 184) = 39.43, p b .001, η2p=.20, with a large decrease occurring in the high-scoring BCS group. However, this group still had higher scores at discharge than the rest of the sample. As shown in Fig. 1, a main effect of time was demonstrated for each of the psychological measures: ASI, F(1, 184) = 12.80, p b .001, η2p=.08; BDI-II, F(1, 93) = 43.75, p b .001, η2p=.41; PHQ-9, F(1, 89) = 28.98, p b .001, η2p =.30; and CSES, F(1, 184) = 40.99, p b .001, η2p=.32, as was a significant group main effect for the ASI, F(1, 184) = 39.31, p b .001, η2p=.20; PHQ-9, F(1, 89) = 6.23, p = .015, η2p=.08; and CSES, F(1, 184) = 6.66, p = .012, η2p =.07. In each case, participants in the upper quartile BCS group had higher scores, both at admission and discharge. Although no significant group main effect was demonstrated with the BDI-II, a trend was observed, p = .094, as was a significant interaction, F(1, 93) = 5.73, p = .02, η2p=.09. Patients in the upper quartile of BCS scores had higher BDI scores at admission, but not at discharge. This was not replicated with the participants who had completed the PHQ-9. On the functional measures, there were significant improvements over time for the 6MWT, F(1, 90) = 14.61, p b .001, η2p=.14; NSWT, F(1, 184) = 134.88, p b .001, η2p=.37 and stairs test, F(1, 184) = 59.86, p b .001, η2p = .23, but no significant group effects, ps N .05. However, a significant Group × Time interaction was found with the stairs test, F(1, 184) = 3.88, p = .05, η2p=.02. An independent samples t-test of change scores revealed that, on average, participants in the upper quartile BCS group showed a significantly greater degree of improvement on the stairs, t(240) = 1.97, p = .05.
The first goal of this study was to validate the BCS, a measure of breathlessness catastrophizing derived from the widely used PCS [18] for pain research, with a relatively large sample of patients undergoing pulmonary rehabilitation for COPD. The results indicated that the BCS consists of a single factor, to which all 13 items contribute, and yields a scale with excellent internal consistency. It is noteworthy that the BCS comprises a single factor, which is different than the three-factor structure of rumination, magnification, and helplessness that characterizes the PCS in chronic pain [18]. Whereas some other studies have demonstrated a one-factor structure to the PCS [45], and most focus on the total score, the contrasting factor structures of the BCS and PCS suggest that there may be differences in the underlying phenomenon of catastrophizing when an individual is experiencing breathlessness, rather than pain. The second goal was to examine the relationship between breathlessness catastrophizing and measures of anxiety sensitivity, depression, selfefficacy, lung function, and exercise performance. Analyses of the baseline data showed that the BCS was correlated with the other self-report measures of psychological constructs. With regard to respiratory measures, the BCS showed a weak correlation with the FVC, but did not correlate significantly with the FEV1. Finally, the BCS did not correlate significantly with the baseline measures of exercise performance. Overall, therefore, the BCS shows convergent validity in its associations with other measures of psychological distress, but has the advantage of specificity to the cognitive reaction to dyspnea. Therefore, it is of more direct relevance to the experience of patients with COPD. In contrast to the present findings, others have reported that constructs pertaining more directly to psychopathology, such as anxiety, panic and depression, do correlate with functional measures [3,9,11, 12,16,34]. One possible explanation is that those findings reflect more severe psychological disorders. For example, fatigue and psychomotor retardation are symptoms of depressive disorders that could impair exercise performance [58], but are not addressed by the more cognitive focus on catastrophizing. Similarly, the experience of panic may have more pervasive functional consequences. In addition, different studies have assessed functional performance in different ways. Self-reports of function may reflect common method variance with self-reports of psychological states, perhaps inflating the correlations when compared to performance-based measures. Indeed, many previous studies have used a self-report format for assessing function [31,59,60]. It should also be noted that structured performance tasks, while important for assessing outcome in a standardized way, may not provide the optimal protocol for demonstrating the role of cognitive processes in COPD. Catastrophic concerns about breathlessness may be more evident in self-selected activities in which avoidance is an option, rather than in supervised therapeutic tasks that place a high priority on patient safety. If so, then decisions about participating in, or avoiding, an activity, and the confidence versus fearfulness with which one engages in it, may be more closely related to catastrophizing than performance measures achieved under supervision. The significant correlation between scores on the BCS and the CSES offers some support for this possibility. On the other hand, neither BCS scores nor any other measure predicted program withdrawal, which could be construed as a form of avoidance for some patients. In general, therefore, there was no clear evidence from the baseline data of an association between catastrophizing and functional performance. Future research could consider such issues as engagement in the rehabilitation process and naturalistic studies of participation in self-selected activities. The final goal of the study was to examine change over time following pulmonary rehabilitation. In this context, the results indicated that BCS scores, as well as other psychological measures, improved significantly following participation in the program. There were also reliable improvements in the measures of exercise performance. Moreover, the analyses
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64
39
48 ASI Score
BCS Score
B.K. Solomon et al. / Journal of Psychosomatic Research 79 (2015) 62–68
26 13
32 16
0
0 Admission
Discharge
20
10
16
8 PHQ-9 Score
BDI-II Score
67
12 8 4
Admission
Discharge
Admission
Discharge
Admission
Discharge
6 4 2
0
0 Admission
Discharge
170
49 42 Stairs Score
CSES Score
136 102 68
35 28 21 14 7
34
0 Admission
Discharge
Fig. 1. Admission and discharge scores by time and BCS group. Solid lines represent the upper quartile BCS group; dashed lines represent the rest of the sample. (BCS = Breathlessness Catastrophizing Scale, ASI = Anxiety Sensitivity Index, BDI-II = Beck Depression Inventory-II, PHQ-9 = 9-Item Patient Health Questionnaire, CSES = COPD Self-Efficacy Scale; BCS, ASI, CSES, Stairs: n = 186; BDI-II: n = 95; PHQ-9: n = 91.).
focusing on the participants in the highest quartile of BCS scores did suggest an association between catastrophizing and functional progress with rehabilitation. On the stair-climbing test, the high catastrophizing patients had more pronounced improvement from pre- to post-treatment, although comparisons at either time point alone did not differ between the groups. This finding offers tentative support for the hypothesis that catastrophizing may be related to participation in the process of rehabilitation. Nevertheless, it should be noted that this conclusion is based on a small effect on a single measure of functional outcome. Therefore, it requires confirmation in future research. More generally, however, it appears evident from the present study that catastrophizing is not a barrier to functional change; even those with the highest levels of breathlessness catastrophizing can make meaningful functional gains with interdisciplinary pulmonary rehabilitation. Conflict of Interest The authors have no competing interests to report.
Acknowledgments Brahm K. Solomon was supported by a Frederick Banting and Charles Best Canada Graduate Scholarships Doctoral Award from the Canadian Insitutes of Health Research (GSD-104600). This study was funded by the same award. Special thanks to Carole LeBlanc and Kathy Walker of The Ottawa Hospital CANVent Program, as well as Nancy Kukulka and Lyne Lavallée of The Ottawa Hospital Rehabilitation Centre Physiotherapy Program. We would also like to thank Dr. Michael J.L. Sullivan, for supporting the adaptation of the Pain Catastrophizing Scale.
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Contents lists available at ScienceDirect
Journal of Psychosomatic Research
A Breathlessness Catastrophizing Scale for chronic obstructive pulmonary disease☆ Brahm K. Solomon a,⁎, Keith G. Wilson b, Peter R. Henderson b, Patricia A. Poulin c, John Kowal b, Douglas A. McKim d a
School of Psychology, University of Ottawa, Canada Department of Psychology, The Ottawa Hospital Rehabilitation Centre, Canada Department of Psychology, The Ottawa Hospital, Canada d Department of Medicine, University of Ottawa, Canada b c
a r t i c l e
i n f o
Article history: Received 17 July 2014 Received in revised form 22 November 2014 Accepted 25 November 2014 Keywords: Catastrophizing Chronic obstructive pulmonary disease Disability Rehabilitation Depression Anxiety
a b s t r a c t Objective: Catastrophizing about breathlessness may be related to disability in patients with chronic obstructive pulmonary disease (COPD), but assessment options are limited. This study reports the initial validation of a 13item Breathlessness Catastrophizing Scale (BCS). Method: Pulmonary rehabilitation inpatients completed spirometric, functional performance and questionnaire assessments at admission (N = 242) and discharge (n = 186). Results: The BCS comprised a unifactorial scale that demonstrated excellent internal consistency (Cronbach's alpha = .96) and correlated with measures of anxiety sensitivity, depression, and self-efficacy, but not with performance on walk and stair-climbing tests. BCS scores improved robustly with rehabilitation, approaching a medium effect size (d = .43), and demonstrated a modest association with enhanced performance in a stairclimbing test of exercise tolerance. Conclusion: The BCS is a reliable measure of catastrophizing in severe COPD that has good convergent validity and sensitivity to change. Its association with functional performance requires further investigation. However, it appears that a high level of catastrophizing about breathlessness is not a barrier to functional improvement with inpatient pulmonary rehabilitation. © 2014 Elsevier Inc. All rights reserved.
Introduction Chronic Obstructive Pulmonary Disease (COPD) is a progressive degenerative lung disease that causes cough, sputum production, and disabling breathlessness [1]. As of 2010, COPD was identified as the fourth leading cause of death in the U.S. and the sixth leading cause of years lived with disability [2]. For those COPD patients who are limited functionally by dyspnea, the recommended treatment includes pulmonary rehabilitation to improve symptom management and participation in activities of daily living [1]. According to the WHO-endorsed standards outlined by Global Initiative for Chronic Obstructive Lung Disease (GOLD) [1], spirometric assessment of lung function is required to confirm a
☆ Clinical and research work was conducted at The Ottawa Hospital Rehabilitation Centre, Ottawa, Ontario, Canada. ⁎ Corresponding author at: School of Psychology, University of Ottawa, Department of Psychology, The Ottawa Hospital Rehabilitation Centre, 505 Smyth Road, Ottawa, ON K1H 8M2, Canada. Tel.: +1 613 422 1870; fax: +1 613 737 7056. E-mail address: [email protected] (B.K. Solomon).
http://dx.doi.org/10.1016/j.jpsychores.2014.11.020 0022-3999/© 2014 Elsevier Inc. All rights reserved.
diagnosis of COPD. Spirometry, however, is often a poor predictor of a patient's level of disability [3]. In contrast, psychological factors have often been related to functional outcomes in this population [4]. Depressive symptoms, for example, have been associated with decreased mobility and functional status [5–10], as well as more frequent and longer hospital admissions [9]. Similarly, anxiety has been related to decreased physical health, exercise performance [3], functional performance status [3,11,12], and more frequent hospitalization [3]. Recently, research has begun to expand beyond broad psychopathological constructs, such as depression and anxiety, into particular affective and cognitive processes that may influence how one attends and responds specifically to the symptom of dyspnea [13, 14]. It has been proposed that breathlessness catastrophizing is one such cognitive process that warrants further investigation [7, 15–17]. Catastrophizing is an exaggerated negative cognitive orientation toward noxious stimuli and experiences, characterized by rumination about those experiences, magnification of their threat value, and perceived inability to control them [18]. It has been associated with measures of disability in other chronic medical conditions,
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particularly chronic pain [19–23]. In some studies of individuals with chronic pain, catastrophizing has been found to be more strongly correlated with disability than the pain itself [24,25]. This has contributed to the development of a fear-avoidance model of disability [26]. The fear-avoidance model proposes that when a symptom is appraised as threatening, the individual may respond with fear, hypervigilance, and avoidance of activity that could trigger it. In the long term, these responses are counterproductive for rehabilitative efforts and can lead to further disability [26]. Indeed, catastrophizing has been identified as a prospective marker of risk for severe disability in chronic pain [27,28], in part leading to the recommendation that the assessment and treatment of catastrophizing should be a regular part of patient care [29,30]. The conceptual link between catastrophizing and disability can perhaps be extended to other medical conditions that feature a prominent primary symptom. In the case of COPD, for example, it would be expected that patients who catastrophize about dyspnea would similarly become fearful of, or hypervigilant to, the experience of breathlessness, perhaps leading to an avoidance of activities that might trigger shortness of breath [31–33]. To date, however, speculation about the importance of catastrophizing in COPD has focused largely on its relevance to the emergence of panic symptomatology that occurs in some patients [16,34]. More generally, a fear-avoidance model applied to COPD would suggest that individuals who catastrophize would engage in physical therapy at suboptimal levels and exhibit a more general unwillingness to engage in programs that are heavily focused on exercise [14]. However, there are limited options for assessing catastrophizing in individuals with COPD, so there has been little formal investigation of these hypotheses. At present, the Interpretation of Breathing Problems Questionnaire (IBPQ) [35] is the sole catastrophizing measure available for use with individuals with COPD. Its format makes it difficult to complete in a clinical setting, however, and it has seldom been used since its development in 1999 [17,36–38]. The IBPQ presents 14 scenarios (e.g., “You are in a smoky pub and your chest begins to feel tight.”) and asks respondents to answer qualitative questions that are subsequently scored by raters for degree of catastrophizing. IBPQ items have been found to correlate with measures of anxiety [35], although not consistently [36]. Moreover, no studies have examined the association between IBPQ scores and functional measures. In the present study, the Breathlessness Catastrophizing Scale (BCS) is proposed as an alternative measure offering several advantages. First, the BCS items directly reflect experiential aspects of catastrophizing (e.g., “There's nothing I can do to reduce the intensity of the breathlessness”). Second, qualification as catastrophic thinking is not limited to an increase in anxiety, illness, or death. Third, the BCS is practical for clinical use, with each item requiring only a single quantitative rating. Finally, the BCS is a modification of the well-established Pain Catastrophizing Scale (PCS) [18], which represents the standard in the assessment of catastrophizing among patients with chronic pain. Given the emerging focus on catastrophizing and anxiety-related concerns in COPD, the goals of the present study were to: (1) validate the scores on the BCS in a relatively large sample of patients undergoing pulmonary rehabilitation for COPD; (2) examine the relationship between breathlessness catastrophizing and measures of anxiety sensitivity, depression, self-efficacy, lung function, and performance in structured physical tasks; (3) examine whether breathlessness catastrophizing changes with participation in a pulmonary rehabilitation program; and (4) evaluate whether breathlessness catastrophizing is related to change in other rehabilitation outcomes. Specifically, we hypothesized that individuals with high levels of catastrophizing would show less improvement in psychological and physical function following interdisciplinary treatment.
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Method Participants The study was approved by the Ottawa Health Science Network Research Ethics Board. Participants were 242 patients with COPD admitted to an inpatient, interdisciplinary pulmonary rehabilitation program at The Ottawa Hospital Rehabilitation Centre (TOHRC; Ottawa, Canada). In order to be eligible for admission to the program, patients had to be referred by a physician, 18 years of age or older, seeking to improve quality of life limited by shortness of breath, cognitively able to learn how to better manage the condition, and meet at least one of the following criteria: (1) FEV1 ≤ 70%; (2) hospitalized recently or visited an emergency department due to dyspnea; (3) willing and able to initiate and maintain an exercise program; (4) using supplemental oxygen. Patients admitted to the program were included in this study if they had completed a BCS at admission. Design Chart reviews were conducted for eligible patients who participated in the program between 2007 and 2011. Extracted data included assessment of lung function, functional measures of exercise performance, and psychometric measures of catastrophizing, anxiety sensitivity, depression, and COPD self-efficacy. Measures completed at both program admission and discharge were collected. Pulmonary rehabilitation program Patients participated in a structured inpatient interdisciplinary pulmonary rehabilitation program based on GOLD and Canadian Thoracic Society guidelines [39,40]. The program took place over four 5-day weeks, with patients returning home over weekends. Measurements Spirometry Forced vital capacity (FVC) is the volume of air that can forcibly be exhaled after full inspiration, measured in liters. Forced expiratory volume in one second (FEV 1 ) is the volume of air that can be forcibly exhaled in 1 s, after full inspiration. These values were measured using a Profiler and CPSF/D spirometer (Medical Graphic Corporation; St. Paul, MN, US). Predicted values for these measurements (FVC%, FEV 1 %) were based on reference values of pulmonary function tests of a Canadian sample [41]. Exercise performance Six-Minute Walk Test The Six-Minute Walk Test (6MWT) is the standard measure of functional capacity used in pulmonary and rehabilitation studies [42]. The test requires a 100-foot flat, hard surface on which individuals can walk unaccompanied. Patients are asked to walk as far as possible in 6 min, slowing, stopping, or resting, as needed. The primary outcome of interest is the distance walked. Contraindications include chest pain, intolerable dyspnea, leg cramps, staggering, diaphoresis, and pale or ashen appearance [42]. Contraindications were common in this sample, and only 98 patients completed the 6MWT at admission. Non-Stop Walk Test The Non-Stop Walk Test (NSWT) is an alternative measure used in the pulmonary rehabilitation program at TOHRC. In line with the
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findings of the developers of the 6MWT [43], longer intervals are considered preferable, when feasible. Patients are asked to walk for 20 min and are encouraged to use a comfortable, self-selected pace with slowing, but no pauses, rests or actual stops. Again, the primary outcome is the distance walked. All 242 patients completed this test at admission. Stair climbing Stair climbing is a standard measure of functional capacity used in cardiac, pulmonary, and rehabilitation studies, and it is considered reflective of a primary activity of daily living and mobility [44]. The present assessments required that the patient climbs as many steps as possible before having to stop because of dyspnea. The total number of stairs climbed was the primary outcome, with a maximum score of 49.
demonstrated excellent internal consistency (Cronbach's α = .86–.89) and test–retest reliability (r = .84) (Kroenke, Spitzer, & Williams, 2001). Cronbach's α for the current sample = .87 (average inter-item correlation = .33). COPD self-efficacy The COPD Self-Efficacy Scale (CSES) [54] is a 34-item self-report questionnaire that assesses individuals' perceived confidence in their ability to manage or avoid breathing difficulties in various situations. Each item is rated along a five-point scale, ranging from 1 (Very Confident) to 5 (Not At All Confident). An overall measure of self-efficacy can be derived as a total score, with higher scores reflecting lower self-efficacy. Internal consistency (Cronbach's α of .95) and test-reliability (r = .77) were reported to be satisfactory [54]. Cronbach's α for the current sample = .96 (average inter-item correlation = .42).
Questionnaire measures Data analysis Breathlessness catastrophizing The BCS was adapted from the PCS [18] by replacing the term “pain” with “breathlessness,” where relevant. The resulting measure is a 13item scale that asks respondents to rate “the degree to which you have these thoughts and feelings when you are experiencing breathlessness” (e.g., “I feel I can't go on”; “It's terrible and I think it's never going to get any better”). Each item is rated on a five-point scale, ranging from 0 (Not At All) to 4 (All The Time). The original PCS has been found to have high test–retest reliability (Pearson's r = .92) [18] and good internal consistency (Cronbach's α s between .85 and .91) [18]. The PCS has been found to have a moderate correlation with selfreport measures of anxiety (r = .32) [45] and anxiety sensitivity (r = .61) [46]. Anxiety sensitivity Anxiety sensitivity is the fear of physiological symptoms of anxiety due to the belief that they are harmful. Studies suggest that anxiety sensitivity promotes hypervigilance to bodily sensations and fearful interpretations of symptoms when they occur [47,48]. Among patients with COPD, anxiety sensitivity has been found to predict greater dyspnea-related activity avoidance, even after controlling for diagnosed anxiety disorders and degree of pulmonary dysfunction [31]. The Anxiety Sensitivity Index (ASI) [34] is a 16item self-report questionnaire that assesses individuals' fear of anxiety-related symptoms. Each item is rated on a five-point scale, ranging from 0 (Very Little) to 4 (Very Much). Overall, the ASI has very good construct validity [49], internal consistency (Cronbach's α of .82–.91) [50], and test–retest reliability over a three-year period (r = .71) [51]. Cronbach's α for the current sample = .93 (average inter-item correlation = .45). Depression During the period of data collection, the respiratory rehabilitation program used two different measures of depression at different times. For part of the sample (n = 124), the 21-item Beck Depression Inventory-II (BDI-II) [52] was used to assess the presence and severity of depressive symptoms. Responses to each item are rated on a 4-point scale, ranging from 0 to 3, with higher scores reflecting more severe symptomatology. The BDI-II has been found to have high internal consistency (Cronbach's α = .91) [52], as well as good convergent validity when correlated with other measures of depression. Cronbach's α for the current sample = .88 (average inter-item correlation = .27). For the rest of the sample (n = 118), depressive symptoms were assessed using the 9-item Patient Health Questionnaire (PHQ-9) [53]. On this measure, respondents rate how often they have been bothered by each of several diagnostically relevant symptoms. Responses are recorded on a 4-point scale, ranging from 0 (Not At All) to 3 (Nearly Every Day). The PHQ-9 has
Statistical analyses consisted of five distinct parts. First, comparisons were undertaken between program completers and noncompleters, using chi-square analyses for categorical measures and independent samples t-tests for continuous ones. Second, for initial construct validation of the BCS, a principal component analysis (PCA) was conducted to examine the underlying factor structure of the catastrophizing items. PCA is considered to provide the best explanation of data variance without requiring a priori assumptions about the nature of the factor structure [55]. Third, to assess the relationship between breathlessness catastrophizing and other baseline measures, a series of bivariate correlations were examined. Fourth, to identify the extent of change in breathlessness catastrophizing and other measures following pulmonary rehabilitation, data collected from program completers at admission and discharge were compared using paired-samples t-tests. Fifth, subgroups were created based on BCS scores at admission. Clinically, BCS scores are likely to be most informative for identifying individuals who are highly prone to catastrophizing. Hence, we selected patients in the upper quartile of BCS scores and compared them with all others in the sample [56]. Admission and discharge data were compared using 2 (Group) X 2 (Time) Analyses of Variance (ANOVA). All analyses were conducted using SPSS version 20. Significance was set at p b .05. Results Sample characteristics Of the 242 patients (n = 126 women, 52%), most had very severe (Stage IV: n = 140, 58%) or severe (Stage III: n = 70, 29%) COPD, based on FEV1 percent predicted staging [1]. Baseline characteristics of the sample are provided in Table 1. Fifty-six patients (23%) did not complete the program. No significant differences were demonstrated between treatment completers and noncompleters. Validation of the BCS Item-level analysis Although individual distributions varied across items, each value on the 5-point scale was used for all 13 items. The mean, standard deviation, and itemtotal correlation for each question on the BCS are presented in Table 2. Notably, there were no negative item-total correlations. Therefore, no item detracted from the cohesiveness of the total BCS scale. Across the 13 items, Cronbach's alpha was .96 (average inter-item correlation = .64), demonstrating excellent internal consistency. The average total score was 18.25 (SD = 11.76), and the score distribution ranged from 0 to 52, the lowest and highest scores possible. There were seven individuals with scores of 0, suggesting no breathlessness catastrophizing in less than 3% of program participants. The overall average item rating on the 13-item scale was 1.44, which falls between “slight” and “moderate” agreement. Question 8 (“I anxiously want the breathlessness to go away”) was the most highly rated (M = 2.05), whereas question 5 (“I feel I can't stand it anymore”) was rated lowest (M = 1.09).
B.K. Solomon et al. / Journal of Psychosomatic Research 79 (2015) 62–68
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Table 1 Baseline characteristics of patients. Total sample (N = 242) Characteristic
M
SD
Age (years) Sex Female Male FEV1, % predicted FVC, % predicted COPD severity Stage I Stage II Stage III Stage IV Oxygen prescription 6MWT, ma NSWT, m Stairs, steps BCS ASI BDI-IIb PHQ-9b CSES
66.1
11.2
n
126 116 41.0 60.7
Completers (n = 186) %
92.6 363.6 13.7 11.8 11.6 7.7 4.7 14.2
SD
65.8
10.7
124b 118b
%
101 85 41.5 61.3
0 32 70 140 58 98a
Non-completers (n = 56)
n
52.1 47.9
19.5 18.6
311.9 447.9 20.1 18.2 21.7 12.0 5.7 106.7
M
SD
67.0
13.2
54.3 45.7
19.9 19.0
39.3 58.7
0.0 13.2 28.9 57.9 24.0 308.7 451.7 19.7 18.7 22.3 11.4 5.7 106.2
M
0 24 52 110 45 92a
89.9 360.1 13.2 12.2 11.9 7.6 4.2 14.7
%
24 32
42.9 57.1
0 8 18 30 13 6a
0.0 14.3 32.1 53.6 23.2
18.2 17.3
0.0 12.9 28.0 59.1 24.2 326.1 435.4 21.6 17.0 19.6 14.1 5.5 108.2
95b 91b
n
105.4 378.2 15.6 10.2 10.3 7.7 6.2 12.4
29b 27b
Note. FEV1 = forced expiratory volume in one second; FVC = forced vital capacity; 6MWT = Six-Minute Walk Test; NSWT = Non-Stop Walk Test; BCS = Breathlessness Catastrophizing Scale; ASI = Anxiety Sensitivity Index; BDI-II = Beck Depression Inventory-II; PHQ-9 = 9-Item Patient Health Questionnaire; CSES = COPD Self-Efficacy Scale. a Due to clinical considerations not all patients completed the 6MWT. b During the period of data collection, the program used two different measures of depression at different times. Therefore patients received either the BDI-II or the PHQ-9. Factor analysis No constraints were placed on the principal component analysis. The eigenvalue for the first principal component was 8.74, declining sharply to 0.75 for the second. This suggested a one component structure. All items loaded on this single component, with loadings ranging from .73 to .88 (see Table 2).
Relationships between breathlessness catastrophizing and other study variables Demographics Bivariate correlations of BCS with gender and age revealed no significant relationships.
Table 2 Item-level analysis and principal component loadings of the Breathlessness Catastrophizing Scale items.
M
SD
Item-total Correlation
Component Loading
1.48 1.13 1.40 1.36 1.09 1.78 1.23 2.05 1.21 1.34 1.68 1.29 1.64
1.14 1.15 1.26 1.24 1.19 1.28 1.22 1.31 1.22 1.19 1.34 1.17 1.34
0.74 0.75 0.85 0.86 0.81 0.82 0.71 0.76 0.80 0.77 0.83 0.69 0.83
0.78 0.79 0.88 0.88 0.84 0.85 0.75 0.79 0.83 0.80 0.86 0.73 0.86
Breathlessness Catastrophizing Scale Items 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12. 13.
I worry all the time about whether the breathlessness will subside. I feel I can't go on. It's terrible and I think it's never going to get any better. It's awful and I feel that it overwhelms me. I feel I can't stand it anymore. I become afraid that the breathlessness will get worse. I keep thinking of other times I have been breathless. I anxiously want the breathlessness to go away. I can't seem to keep it out of my mind. I keep thinking about how out of breath I am. I keep thinking about how badly I want the breathlessness to stop. There's nothing I can do to reduce the intensity of the breathlessness. I wonder whether something serious might happen.
Note. Cronbach's alpha = .96 (average inter-item correlation = .64). Item ratings ranged from 0 (“Not At All”) to 4 (“All The Time”.)
Table 3 Correlations between measures at baseline.
BCS ASI BDI-IIa PHQ-9a CSES FEV1% FVC% 6MWTa NSWT Stairs
BCS
ASI
– .61⁎⁎⁎ .50⁎⁎⁎ .42⁎⁎⁎ .34⁎⁎⁎ −.12 −.19⁎⁎ −.15 −.11 −.10
– .52⁎⁎⁎ .51⁎⁎⁎ .30⁎⁎⁎ .06 −.08 −.06 −.05 −.12
BDI-IIa
PHQ-9a
CSES
FEV1%
FVC%
6MWTa
NSWT
– .19 .05 .13 −.28 −.09 −.11
– −.04 −.09 .15 .02 −.02
– .60⁎⁎⁎ .29⁎⁎ .12 .03
– .30⁎⁎ .19⁎⁎ .21⁎⁎
– .61⁎⁎⁎ .43⁎⁎⁎
– .56⁎⁎⁎
– b
.36⁎⁎⁎ −.01 −.25⁎ .07 −.07 −.09
Note. N = 242. a Due to program and clinical considerations not all patients completed all measures included here: BDI-II (n = 124); PHQ-9 (n = 118), 6MWT (n = 98). b During the period of data collection, the program used two different measures of depression at different times. Therefore patients received either the BDI-II or the PHQ-9. ⁎ p b .05, two-tailed. ⁎⁎ p b .01, two-tailed. ⁎⁎⁎ p b .001, two-tailed.
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Discussion
Table 4 Change in outcome measures from admission to discharge. Admission Variable FEV1, % predicted FVC, % predicted 6MWT, ma NSWT, m Stairs, steps BCS ASI BDI-IIa PHQ-9a CSES
Discharge
Change
M
SD
M
SD
t
p
db
41.85 62.08 313.04 447.59 20.24 18.13 21.85 11.25 5.76 104.43
20.16 18.15 94.42 362.19 14.12 11.70 12.21 7.76 4.23 18.37
42.67 62.42 344.68 677.50 26.68 13.30 18.85 6.70 2.68 84.02
20.81 18.12 85.75 293.52 19.04 11.50 13.06 6.47 3.32 28.79
1.16 0.35 4.48 12.87 7.65 −6.14 −3.33 −6.08 −6.41 −7.31
.248 .725 b.001 b.001 b.001 b.001 .001 b.001 b.001 b.001
0.04 0.02 0.35 0.70 0.38 0.42 0.24 0.64 0.81 0.85
Note. n = 186. FEV1 = forced expiratory volume in one second; FVC = forced vital capacity; 6MWT = Six-Minute Walk Test; NSWT = Non-Stop Walk Test; BCS = Breathlessness Catastrophizing Scale; ASI = Anxiety Sensitivity Index; BDI-II = Beck Depression Inventory-II; PHQ-9 = 9-Item Patient Health Questionnaire; CSES = COPD Self-Efficacy Scale. a Due to clinical and program considerations not all patients completed all measures included here: 6MWT (n = 92); BDI-II (n = 95); PHQ-9 (n = 91). b d = Cohen's d where .20, .50, and .80 represent small, medium and large effects, respectively. Psychological variables At program admission, BCS scores were moderately and positively correlated with anxiety sensitivity, depressive symptomatology, as measured by either the BDI-II or the PHQ-9, and scores on the CSES, indicating lower sense of self-efficacy at managing or avoiding breathing difficulty (see Table 3). Respiratory function At baseline only FVC% correlated with BCS scores. Although statistically significant, the correlation was small in magnitude (r = −.19, p = .004). There was no association between BCS scores and prescribed oxygen. Exercise performance Breathlessness catastrophizing was not significantly correlated with the baseline measures of exercise performance (all ps N .10). However, both walk tests and the stairs exercise were correlated significantly with one another (ps b .01) and with the FVC%. In addition, performance on the 6MWT was correlated significantly with the FEV1%. Outcome of pulmonary rehabilitation The pre- and post-rehabilitation scores for all measures of respiratory function, exercise performance, and psychological variables are shown in Table 4. From admission to discharge, spirometry did not reveal any significant change in lung function, ps N .05. However, patients improved on all measures of physical and psychological functioning, including scores on the BCS, p ≤ .001. The change in BCS scores approaches a medium effect size, d = .43 [57]. Group comparisons based on BCS scores at admission To examine the clinical relevance of the BCS for rehabilitation in COPD, the subgroup of participants who fell in the upper quartile of BCS scores at admission was compared with the rest of the sample. The scores are shown in Fig. 1. In addition to the main effect of group, F(1, 184) = 138.61, p b .001, η2p=.47, these scores showed a significant main effect of time, F(1,184) = 82.17, p b .001, η2p=.34, indicating an overall decrease following rehabilitation. The Group × Time interaction was also significant, F(1, 184) = 39.43, p b .001, η2p=.20, with a large decrease occurring in the high-scoring BCS group. However, this group still had higher scores at discharge than the rest of the sample. As shown in Fig. 1, a main effect of time was demonstrated for each of the psychological measures: ASI, F(1, 184) = 12.80, p b .001, η2p=.08; BDI-II, F(1, 93) = 43.75, p b .001, η2p=.41; PHQ-9, F(1, 89) = 28.98, p b .001, η2p =.30; and CSES, F(1, 184) = 40.99, p b .001, η2p=.32, as was a significant group main effect for the ASI, F(1, 184) = 39.31, p b .001, η2p=.20; PHQ-9, F(1, 89) = 6.23, p = .015, η2p=.08; and CSES, F(1, 184) = 6.66, p = .012, η2p =.07. In each case, participants in the upper quartile BCS group had higher scores, both at admission and discharge. Although no significant group main effect was demonstrated with the BDI-II, a trend was observed, p = .094, as was a significant interaction, F(1, 93) = 5.73, p = .02, η2p=.09. Patients in the upper quartile of BCS scores had higher BDI scores at admission, but not at discharge. This was not replicated with the participants who had completed the PHQ-9. On the functional measures, there were significant improvements over time for the 6MWT, F(1, 90) = 14.61, p b .001, η2p=.14; NSWT, F(1, 184) = 134.88, p b .001, η2p=.37 and stairs test, F(1, 184) = 59.86, p b .001, η2p = .23, but no significant group effects, ps N .05. However, a significant Group × Time interaction was found with the stairs test, F(1, 184) = 3.88, p = .05, η2p=.02. An independent samples t-test of change scores revealed that, on average, participants in the upper quartile BCS group showed a significantly greater degree of improvement on the stairs, t(240) = 1.97, p = .05.
The first goal of this study was to validate the BCS, a measure of breathlessness catastrophizing derived from the widely used PCS [18] for pain research, with a relatively large sample of patients undergoing pulmonary rehabilitation for COPD. The results indicated that the BCS consists of a single factor, to which all 13 items contribute, and yields a scale with excellent internal consistency. It is noteworthy that the BCS comprises a single factor, which is different than the three-factor structure of rumination, magnification, and helplessness that characterizes the PCS in chronic pain [18]. Whereas some other studies have demonstrated a one-factor structure to the PCS [45], and most focus on the total score, the contrasting factor structures of the BCS and PCS suggest that there may be differences in the underlying phenomenon of catastrophizing when an individual is experiencing breathlessness, rather than pain. The second goal was to examine the relationship between breathlessness catastrophizing and measures of anxiety sensitivity, depression, selfefficacy, lung function, and exercise performance. Analyses of the baseline data showed that the BCS was correlated with the other self-report measures of psychological constructs. With regard to respiratory measures, the BCS showed a weak correlation with the FVC, but did not correlate significantly with the FEV1. Finally, the BCS did not correlate significantly with the baseline measures of exercise performance. Overall, therefore, the BCS shows convergent validity in its associations with other measures of psychological distress, but has the advantage of specificity to the cognitive reaction to dyspnea. Therefore, it is of more direct relevance to the experience of patients with COPD. In contrast to the present findings, others have reported that constructs pertaining more directly to psychopathology, such as anxiety, panic and depression, do correlate with functional measures [3,9,11, 12,16,34]. One possible explanation is that those findings reflect more severe psychological disorders. For example, fatigue and psychomotor retardation are symptoms of depressive disorders that could impair exercise performance [58], but are not addressed by the more cognitive focus on catastrophizing. Similarly, the experience of panic may have more pervasive functional consequences. In addition, different studies have assessed functional performance in different ways. Self-reports of function may reflect common method variance with self-reports of psychological states, perhaps inflating the correlations when compared to performance-based measures. Indeed, many previous studies have used a self-report format for assessing function [31,59,60]. It should also be noted that structured performance tasks, while important for assessing outcome in a standardized way, may not provide the optimal protocol for demonstrating the role of cognitive processes in COPD. Catastrophic concerns about breathlessness may be more evident in self-selected activities in which avoidance is an option, rather than in supervised therapeutic tasks that place a high priority on patient safety. If so, then decisions about participating in, or avoiding, an activity, and the confidence versus fearfulness with which one engages in it, may be more closely related to catastrophizing than performance measures achieved under supervision. The significant correlation between scores on the BCS and the CSES offers some support for this possibility. On the other hand, neither BCS scores nor any other measure predicted program withdrawal, which could be construed as a form of avoidance for some patients. In general, therefore, there was no clear evidence from the baseline data of an association between catastrophizing and functional performance. Future research could consider such issues as engagement in the rehabilitation process and naturalistic studies of participation in self-selected activities. The final goal of the study was to examine change over time following pulmonary rehabilitation. In this context, the results indicated that BCS scores, as well as other psychological measures, improved significantly following participation in the program. There were also reliable improvements in the measures of exercise performance. Moreover, the analyses
52
64
39
48 ASI Score
BCS Score
B.K. Solomon et al. / Journal of Psychosomatic Research 79 (2015) 62–68
26 13
32 16
0
0 Admission
Discharge
20
10
16
8 PHQ-9 Score
BDI-II Score
67
12 8 4
Admission
Discharge
Admission
Discharge
Admission
Discharge
6 4 2
0
0 Admission
Discharge
170
49 42 Stairs Score
CSES Score
136 102 68
35 28 21 14 7
34
0 Admission
Discharge
Fig. 1. Admission and discharge scores by time and BCS group. Solid lines represent the upper quartile BCS group; dashed lines represent the rest of the sample. (BCS = Breathlessness Catastrophizing Scale, ASI = Anxiety Sensitivity Index, BDI-II = Beck Depression Inventory-II, PHQ-9 = 9-Item Patient Health Questionnaire, CSES = COPD Self-Efficacy Scale; BCS, ASI, CSES, Stairs: n = 186; BDI-II: n = 95; PHQ-9: n = 91.).
focusing on the participants in the highest quartile of BCS scores did suggest an association between catastrophizing and functional progress with rehabilitation. On the stair-climbing test, the high catastrophizing patients had more pronounced improvement from pre- to post-treatment, although comparisons at either time point alone did not differ between the groups. This finding offers tentative support for the hypothesis that catastrophizing may be related to participation in the process of rehabilitation. Nevertheless, it should be noted that this conclusion is based on a small effect on a single measure of functional outcome. Therefore, it requires confirmation in future research. More generally, however, it appears evident from the present study that catastrophizing is not a barrier to functional change; even those with the highest levels of breathlessness catastrophizing can make meaningful functional gains with interdisciplinary pulmonary rehabilitation. Conflict of Interest The authors have no competing interests to report.
Acknowledgments Brahm K. Solomon was supported by a Frederick Banting and Charles Best Canada Graduate Scholarships Doctoral Award from the Canadian Insitutes of Health Research (GSD-104600). This study was funded by the same award. Special thanks to Carole LeBlanc and Kathy Walker of The Ottawa Hospital CANVent Program, as well as Nancy Kukulka and Lyne Lavallée of The Ottawa Hospital Rehabilitation Centre Physiotherapy Program. We would also like to thank Dr. Michael J.L. Sullivan, for supporting the adaptation of the Pain Catastrophizing Scale.
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